Phosphorus esters, ocurring as they do in DNA, RNA, certain lipids and many other natural compounds, play key roles in life processes. Most of their synthetic and metastable reactions involve attack at the phosphorus atom by a nucleophile of some sort, for example RO- or RS-. Surprisingly little is known about the effect of the structure and solvation of the nucleophile on the ease of such reactions. In this research the absolute and relative rates of reaction of trimethyl phosphate (CH30)3P0 and of the highly reactive esters methyl metaphosphate (CH30P02) and methyl metaphosphite (CH30P0) with a variety of nucleophiles will be determined in the gas phase. A new and highly verstaile instrument, the flowing afterglow-selected ion flow tube, as well as a conventional flowing afterglow will be used for these studies. The metaphosphate and metaphosphite esters will be generated in a pyrolyzer and introduced in the dilute gas phase. Solvated ions as well as labelled ions and ions of unusual structure can be used an nucleophiles. Sulfur and nitrogen analogs of the esters will also be examined. The chemistry of ions related to these esters, e.g., P03-,P02-,P02S-, will also be studied.